Field
This invention relates to heat and fire protective items, and in particular, to garments and gear that are protective from fire and excessive heat.
Description of the Related Art
Protective garments are used in applications, such as firefighting, law enforcement, military, or industry, where protection of the wearer against heat or flames is required. The protective garment needs to provide a significant degree of thermal insulation against flames and heat, and to suppress heat transfer through the garment from the outside to the inside. The garment also needs to allow some degree of moisture transfer, or breathability through the garment from the inside to the outside. In addition, the protective garment needs to be functional and sufficiently comfortable for the wearer to perform his/her duties.
A protective garment for a firefighter requires sufficient thermal insulation when the firefighter is exposed to flashover of flames where temperatures may reach up to 1000° C. The outer shell of the protective garment is expected to protect the wearer at temperatures up to 350° C. when he/she needs to approach flames closely. However, the interior of the garment next to the wearer's skin should not exceed 38° C.
A known firefighter's protective garment uses intumescent materials. An intumescent substance has a polymer resin-expandable graphite mixture positioned between a flame barrier layer and a liquid-proof barrier layer. At an activation temperature of about 200° C., the volume of the intumescent substance increases. After exposure to about 300° C., the volume increases to about 200%. The intumescent material can be manufactured as discrete guard plates affixed to an outer surface of a flexible fabric. The guard plates expand upon exposure to sufficient heat to provide a continuous thermal insulating and flame retardant outer shell film. The guard plates may also include microcapsules filled with water or a water-based solution that evaporates upon exposure to heat. However, this approach has limitations when applied to fabric and requires a high activation temperature.
Another known firefighter's garment includes multiple cavities filled with a gas generating agent that becomes activated upon reaching its activation temperature. The gas-filled cavities reside between two or more laminar layers. The gas within the cavities expands to provide an insulation layer. However, a gas cavity becomes inoperable if the garment is torn or poked in the area of the gas cavity.